NeuroLog System Applications – Extracellular Recording

The NeuroLog System is a highly versatile modular electrophysiology tool, which can be configured for a multitude of different applications. In this article we examine how it can be used for extracellular recording from microelectrodes, one of the most popular applications that the NeuroLog System is used for.

Low Noise, Compact, Remote Headstage
The NL100AK PREAMPLIFIER HEADSTAGE and NL104A AC PREAMPLIFIER combine to provide an excellent low noise amplification, impedance matched system for extracellular AC recording from in vitro or in vivo preparations. The NL100AK is a compact, cylindrical headstage fitted with a metal manipulator mounting rod and 2m long screened cable. The headstage features a 2mm main input (A-in) socket and 1mm connectors for the reference (B-in)/Ground inputs.

Flexible Amplifier Settings & Signal Conditioning Options
The NL104A can be used in differential or single-ended modes and can amplify a signal by x100 to x20k. A 0.1Hz or 10Hz low frequency cut-off filter allows removal of DC components. If the signal of interest requires further amplification, the NL106 AC/DC AMPLIFIER to boosts the gain by up to x100. Notch (50/60Hz), low and high cut filtering is provided by the NL125 FILTER. The output from the NL125 can be fed directly into a computer via an ADC for data acquisition, or alternatively, individual spikes can be discriminated using the NL201 SPIKE TRIGGER module. The aperture size, polarity and height of the discriminator window can be monitored on an oscilloscope with the raw data superimposed (MONITOR). The various outputs on the NL201 produce a TTL compatible pulse in response to a spike which crosses the lower threshold only (LOWER), upper threshold (UPPER) and lower but not upper thresholds (GATE). These pulses can be collected by a computer DAC enabling spike frequency logging to be carried out.

Often it is desirable to be able to hear the spike activity during an experiment and with the NL120S AUDIO AMPLIFIER and NL985 LOUDSPEAKER, this is possible. As the NL120S has two inputs, it is possible to switch between listening to the raw filtered/amplified signal or the “clicks” resulting from the detection of individual spikes.

Cable-Free Module Communication
This particular configuration of modules requires only one Lemo interconnection cable (NL951), as all other module connections are made internal through the NL900D or NL905 CASE & POWER SUPPLY UNIT. This not only keeps the front of the system free from a tangle of cables, but provides a potentially less noisy method of communication. Additional cables and “T” connectors would be required to feed the signals into a data acquisition system.

Compatible with Multi-Parameter Recording
If you want to make multiple AC-coupled recordings from a single preparation, you can use several sets of some of the modules above in an NL900D rack to record simultaneous EEG, EMG and ECG. If you have a particular application in mind and would like some guidance from our experts, please don’t hesitate to get in touch.